This invention pertains to combustors and more particularly to a simple injector concept for interlocking two or more reactants to provide increased combustion efficiency and to provide a fundamental mechanism for achieving dynamically stable combustion in a wide range of combustor sizes.
One of the greatest problems in reactors such as rocket engines or industrial burners when two reactants are introduced through an injector for mixing, is that of achieving combustion stability. This problem of maintaining combustion stability has been present or can be initiated in nearly all combustors, and particularly as the size of the combustor is inccreased. By using an injector concept in which all of the reactant is introduced into the chamber from the center region of the head end closure plate, the combustion process can be made dynamically stable in all engine sizes. This results from the energy source being located at the nodal point of the acoustic pressure field. However, a fundamental problem exists, particularly with hypergolic fuels, when the injection into the chamber is concentrated at the center of the combustor. This problem with hypergolic fuel combustion is the degree of hydraulic mixing which determines both the fuel distribution and the heat available for vaporization. This mixing becomes increasingly limited as the injector element size is increased. As larger streams or solid sheets of very reactive oxidizer and fuel impinge on each other, prior art engines and combustors experienced only limited liquid mixing before gas and vapor generated at the interface is present in sufficient quantity to partially separate the oxidizer and fuel streams. The result of this is that a certain percentage of the total fuel is deflected apart and remains unmixed, and any further mixing must occur downstream in the combustion chamber either by the relatively slow processes of diffusion or recirculation. This results in decreased combustion efficiency in the engine or combustor. In addition to the problem of not obtaining sufficient mixing with larger element sizes, the concentration of the fuel into relatively unmixed pockets can cause high amplitude local pressure fluctuations if they reach explosion limits. These fluctuations may become quite severe in the fuel-rich regions of the chamber, and in some cases large enough pressure spikes to be destructive of the combustor walls can occur. In addition, these disturbances form the main source of triggers for combustion instability in the chamber.
In prior art structures, the problem of combustion instability has been resolved in some cases by accepting the possibility of the phenomena and statistically assuming that a certain percent of the engines or combustors will fail. Another way of solving this problem has been to provide baffles on the injector face or other types of acoustic energy absorbing devices in the combustion chamber to decrease the tangential or transverse and radial modes of pressure fluctuations. However, with these methods, for each change in combustor size, much design and testing work is necessary to provide the proper baffle or absorber configuration and also to establish the other injector design parameters to provide a matched system. An example of this baffle construction is seen in the U.S. Patent to Mower et al, U.S. Pat. No. 3,200,589.